1. Field of the Invention
This invention relates to a rotary fluid pump in which fluid intake, compression and discharge operations are carried out by the vane movements with the rotation of a rotor. More particularly, the invention relates to a type thereof wherein fluid inlet and/or outlet ports are symmetrically opened at both sides of the rotor chamber.
2. Description of the Prior Art
Within the prior art rotary fluid pumps have been provided with a rotor chamber defined between a main body of a stator housing and end heads assembled at both side faces of the main body. A rotor is rotationally supported within the rotor chamber, and is formed with a plurality of radial vane grooves in which equal plurality of vanes are slidingly engaged. These vanes are rotated by the rotation of the rotor, during which the vanes are moved radially outwardly by the centrifugal force to contact the radially outer ends of the vanes with an inner peripheral surface of the main body. Hence fluid enters from a fluid inlet port into the rotor chamber and is discharged toward a fluid discharge through a fluid outlet port.
Also known is an another type of a rotary fluid pump having a pair of recessed end heads assembled at opposite ends of the housing to form a pump cavity therewith. A pair of resilient sealing plates are individually disposed between the ends of the housing and the recessed end heads to divide the pump cavity into a pair of end chambers defined by the end recessed and the sealing plates and an intermediate rotor chamber defined by the sealing plates. A plurality of vanes are slidingly disposed in an equal plurality of grooves radially formed in a rotor mounted on a drive shaft within the rotor chamber.
According to these conventional rotary fluid pumps, a fluid inlet port is formed in one of the end heads in the former type or formed in one of the sealing plates in the latter type, and fluid outlet port is formed in the other end head or the other sealing plate. Alternatively, fluid inlet and outlet ports are formed in one of the end heads or sealing plates, and no ports are formed in the other end head or sealing plate.
Such conventional pumps have drawbacks. Since fluid is introduced into the rotor chamber from the inlet port formed at one side of the rotor chamber, the vanes are subject to non-uniform intake pressure. Furthermore, since fluid is discharged through the outlet port formed at one side of the rotor chamber, the vanes are also subject to non-uniform fluid discharge pressure. Therefore during operation, the vanes tend to be locally worn out due to non-uniform pressure applied thereto, to thus degrade pump efficiency.